Thermostatic circuit controlling device



g- 1950 J. H. DERBY ETAL 2,516,964

THERMOSTATIC CIRCUIT CONTROLLING DEVICE Filed Nov. 29, 1946* 2Sheets-Sheet l 3noentors Jm/A/ H QE/PBY THOMAS G was gay,

Gttorncp 1950 J. H. DERBY ETAL 2,516,964

THERMOSTATIC CIRCUIT CONTROLLING DEVICE Fi'l-ed Nov; 29,1346 2Sheets-Sheet 2 31mm tors 70H /v D595) 7/70/14; 6. 60.4 4 //V65 GttomegPatented Aug. 1, 1950 THERMOSTATIC CIRC DEVIC UIT CONTROLLING I John H.Derby, Scarsdale, N. Y., and Thomas G. Collings, North Plainfield, N.J., assignors to American Fire Prevention Bureau, Inc., New York, N. Y.,a corporation of New York Application November 29, 1946, Serial No.713,176

3 Claims.

This invention relates to thermostatic circuit controlling devices, andparticularly to thermostatic circuit closers operating upon the broadprinciple of those shown in U. S. Letters Patent No. 1,274,248, grantedJuly 30, 1918, to John H. Derby and Ernest S. Clayton, assignors toAmerican Fire Prevention Bureau, Inc. of New York.

'Circuit closers of the type shown in the Letters Patent aboveidentified, both in the form shown in said Letters Patent and withslight later modifications and improvements, have been extensively andsuccessfully used for both fire alarm and fire prevention purposesthroughout all the years since their invention. The pressure upon thedisk of fusible conducting material in the circuit closer of said priorLetters Patent is produced by the preliminary shaping of the twoterminal disks which, when clamped into the final circuit closerstructure in insulated relation to each other, remain under a stresswhich maintains a pressure upon the disk of fusible conducting materialand thus insures its flow, when fused, through the thin perforatedinsulating disk into short-circuiting relation to the terminal disks.

Thermostatic circuit closers embodying the invention of said priorLetters Patent and designed to operate when the temperature in theregion thereof reaches, say. 152 F., operate with certainty but requirea certain amount of time after the temperature of the surrounding airreaches the desired degree before the fusion of the disk of fusibleconducting material effects the closure of the circuit. This timeelement in the operation of the thermostatic circuit closers of saidprior Letters Patent, as they have been made and perfected in the yearsof their extensive use, has varied from 140 to 150 seconds, that is fromapproximately 2 minutes and 20 seconds to 2 minutes. Although this timeelement does not constitute a drawback to the use of these circuit ofsaid prior Letters Patent but which is so designed and constructed thatthe time element is materially reduced.

, Among the objects of the present invention .is

providing a fixed temperature circuit closer that will operate inappreciably less time than those fusible alloy circuit closers nowgenerally employed and yet which will not be so sensitive as to .givefalse alarms by reason of sudden changes in room temperature having norelation to fire hazards, such, for example, as the opening of a doorbetween a heated room and a cold room, the uncovering of a containercontaining a heated liquid, etc.

As a result of extensive experiments we have discovered that athermostatic circuit closer, of much smaller overall dimensions thanthose made in accordance with the said prior Letters Patent hereinaboveidentified but so constructed that the pressure exerted upon the disk offusible conducting material is not a function of the structure of theterminals but is maintained by special pressure producing means, willoperate to close the circuit in much less time than will a circuitcloser incorporating the general structure of said prior Letters Patent.We have particularly found that, if one circuit terminal be made in theform of a cup, in the bottom of which the disk of conductive alloyfusible at a predetermined temperature is located, and if a perforatedpiston-like disk of insulation be pressed down upon this disk ofconductive alloy by means, for example, of a compressed coil springlocated between the cup closure and the disk of insulation, and if theother terminal be mad in the form of a conductive rod insulated from thecup and extending thereinto into immediate proximity to the insulatingdisk over the perforated part thereof, the whole thermostatic circuitcloser can be made of such dimensions that the overall length of the cupand closure may be less than onehalf inch, in fact considerably lessthan one-half inch, if desired, and its overall diameter alsoconsiderably less than one-half inch and that such a circuit closer willoperate much more quickly to close the circuit by fusion of the disk ofconductive alloy than will a circuit closer embodying the structuralprinciples of said prior Letters Patent.

Not only does the circuit closer of the present invention have importantadvantages over the circuit closer embodying the structural principlesof said prior Letters Patent by reason of the shorter time required forits operation (from seconds to seconds) but it lends itself, by reasonof its overall dimensions, to use in an eiiective substitute for theso-called continuous wire systems such, for example, as those in whichtwisted piano wires are insulated from each other by plastic insulationfusible at predetermined temperatures.

As more fully pointed out hereinafter, the novel thermostatic circuitcloser of the present invention, by reason of its small dimensions, maybe so installed at intervals in a fire detection cable comprising twowires adapted to constitute the two sides of a signal or other firecontrol circuit, said wires being each covered with heatresistinginsulation and being twisted together except at intervals suitablyspaced for fire de tection purposes, that one of these circuit closers,located at each of such intervals and connected to the respective wires,will serve effectively to detect any fire within the spaces to beprotected by the detection circuit. Moreover, its operation can quicklybe determined by suitable indicatin means, such, for example, as thatdisclosed in U. S. Letters Patent No. 1,938,583, granted December 12,1933, to John H. Derby, and the circuit closer, thus easily detected,can be as easily and quickly replaced,

An important feature of the present invention is the arrangement of themeans for exerting constant pressure on the perforated disk ofinsulation and thereby upon the disk of fusible conductive alloy, forexample a coil spring compressed between the cup closure and theperforated disk of insulation, so that it exerts its pressure upon themargin of said disk, thereby insuring fiow of the fused alloy up throughthe perforation in the disk into circuit closing contact with the saidrod, while preventing flow about the periphery of said insulating disk.

Another important feature of the invention is the effective insulation,in a structure of such small overall dimensions, of one terminal fromthe other, both electrically and thermally. Still another feature of theinvention is the effective sealing of all operative parts of thestructure from corrosive gases, dust, moisture and everything else thatmight interfere with their functioning,

Other features, advantages and objects of the invention, to whichreferences has not specifically been made hereinabove, will appearhereinafter when the following description and claims are considered inconnection with the accompanying drawings, in which Figure 1 is a,section on the line 1-4 of Figure 2 showing particularly the details ofconstruction of the novel thermostatic circuit'closer of the presentinvention and also one way of mounting this thermostatic circuit closerfor connection to a circuit including outlet boxes. This figure showsthe parts drawn to an enlarged scale;

Figure 2 is a bottom plan view, substantially to scale, of thethermostatic circuit closer of the present invention and of theinsulating support therefor through which connection is made to anoutlet box in an alarm or other control circuit;

Figure 3 is a section on the line 33 of Figure 2 showing the circuitconnections at the back of the insulating disk or outlet box coverthrough which connection is made to the circuit wires in the outlet box;

Figure 4 is a broken view showing fire detecting cable comprisingtwisted wires, each covered with fire resisting insulation, in whichthermostatic circuit closers, embodying the present invention, areinserted at untwisted intervals along the line of said cable;

Figure 5 is an end View, substantially to the scale of Figure 1, of oneof the thermostaticcir- 4 cuit closers shown in Figure 4, this viewbeing taken from the closure end and having for its purpose to show thelocation of the indicator which indicates the one of the circuit closerswhich has operated;

Figure 6 is a section on the line 6-6 of Figure 7 of a slightly modifiedform of the circuit closer and of the mounting therefor, and

Figure '7 is a plan view of the inside of the outlet box cover shown inFigure 6 and of the circuit connections.

The thermostatic circuit closer of the present invention, shown insection in Figure 1, comprises a cylindrical cup 2 of good conductivematerial for both heat and electricity, such, for example, as brass,this cup having thereon, preferably integral with its bottom, connectivejaws 4 to receive between them a stripped portion of a wire constitutingone side of a fire alarm or other control circuit. These jaws 4 areshown projecting from a shoulder 6, also integral with the bottom of thecup, the purpose. of the shoulder 6 being to form a spacer and terminalcontact portion for the cup bottom when the connection to the circuit isto be made in the manner shown in Figures 1 to 3. The jaws l may bepinched together to grip the wire inserted between them, thus making agood conductive connection, as shown in Figure 5.

Located in the bottom of the cup 2 is a disk 8 of a conductive alloy,fusible at a predetermined temperature, such, for example, as the alloydisclosed in U. S. LettersPatent to John H. Derby, No. 1,982,645 grantedDecember 4, 1934, which is designed to fuse at a temperature from to 152F. The disk 8 preferably fits snugly within the side walls of the cup 2and, as above suggested, rests upon the bottom of the cup. Bearing uponthe otherwise exposed face of the alloy disk 8 is a piston-like disk Inof insulating material, such, for example, as Bakelite, this disk III,as shown, also fitting closely but slidably within the'inner cup walland having a central perforation i2 through which the alloy of the disk8, when fused, may flow into circuit-closing contact with a conductiverod M, of brass or other suitable electrically conductive material,which constitutes the other terminal of the circuit closer and which hason its outer end connective jaws l6, similar to the jaws 4 on the cup 2,these jaws being adapted to receive between them a stripped portion of awire constituting the other side of the fire alarm or other controlcircuit and to be pinched into tight clamping relation thereto. The rod14 is also preferably provided with a shoulder I8 for the same purposeas the shoulder 6 on the cup 2. a i

The conductive rod it passes through a closure 20 of insulatingmaterial, such as Bakelite, which fits closely the inner wallof the cup2 and serves to close and to seal'the otherwise open end of said cup,this closure 20 also having a flange 22 which overlaps and fits tightlyagainst the lip of the cup 2. The conductive rod 14 ispreferably locatedat the center of the closure 20 and is sealed into the Bakelite or otherinsulating material of which the closure 20 ismade, as, for example, bybeing molded thereinto when the closure is molded, and extends, asshown, into immediately proximity to or contact with-the insulation diskH3 over the opening l2 therein.

Between the closure 20 and the insulation disk ID' a coil spring 24,01"any suitable material, such, forexample, as stainless steel, is locatedand is compressed to-a predetermined extent to exert upon the insulationdisk H! the pressure desired or required to insure flow ofthe' alloy ofthe disk 8, when fused, through the perforation l2 in the disk l0. Tomaintain this spring 24 in its compressed condition. and to prevent anychance that the closure 20 might moveout of its closing and sealingrelation to the mouth of the cup-2, the closure 20 is preferablyprovided, on that part of its periphery which lies within and tightlyfits the inner wall of the cup 2, with a groove 26 which may be, asshown, V-shaped in section and into which, after assembling the parts,is rolled a correspondingly shaped rib of the cup 2, as shown-at 28.

In order that the movement of the insulation disk l toward the bottom ofthecup 2 under the action of the spring 24, when the alloy disk 8 fuses,may not open a passagebetween the end of the conductive rod M and theinsulation disk 10 through which the fused alloy might flow into thechamber in which the spring 24 is located, and thus out of circuitclosing contact with the rod i l, the insulation disk 10 is made of athickness, at least around the lower or inner end of the rod it, toprovide a well around the opening 12 in the disk into which the innerend of the conductive rod [4 projects and closely but slidably fits,this well being sufliciently deep so thatimovement of the insulationdisk In under the action of the spring 24 completely to the bottom ofthe cup 2 would not open a passage for the fused alloy between the rod14 and the insulation disk Hi. It will be seen, therefore, that, at alltimes, even if the fusion be so complete and continue so long that theinsulation disk i0 is moved completely to the bottom of the cup 2 byaction of the spring 24, there will still be a conductive orcircuit-closing contact made by the fused alloy 8 through the opening I2between the bottom of the cup 2 and the bottom of the conductive rod 14,the fused alloy being confined in the opening l2 and in the well 30 atall times.

From the foregoing description it will be seen that the circuit closerof the present invention, which, as above pointed out, is shown in Fig.1 of the drawings drawn to an enlarged scale, is so constructed that itsaction is positive and that any expansion of the metal parts thereofincident to the rise in temperature necessary for its operation will inno way affect the positive nature of its operation. By reason of thefact that the cup 2, of a good heat conducting as well as electricallyconductive material, such, for example, as brass, is of a comparativelyrigid construction and is of such overall contour and dimensions thatthe heat received by it from the surrounding air is concentratedprincipally in the region where it is needed for effecting the fusion ofthe alloy disk '8, a fusion of the disk 8, sufiicient to effect circuitclosing by how of the fused material into contact with the conductiverod I4, takes place, as above stated, in much less time (from 70 secondto 90 seconds) than in circuit closers of the prior art which operate onthe same general principle. the fact that, in the much larger circuitclosers of the prior art, there is liability to too great diffusion ofthe heat imparted to the structure from the surrounding air. Moreover,the pressure brought to bear upon the solder in the earlier circuitclosers, although fully effective for its purpose, is probably notproportionately so great. In the structure of the present invention itwill be seen that the spring 24 is confined between the rigid cupclosure 20 and the insulation disk One reason for this is believed to beH] which presses the fusible alloy disk 8 against the fixed andunyielding bottom of the cup 2. It will further be seen that thepressure thus exerted by the spring 24 on the disk Ii] may be sopredetermined that any lengthwise expansion of the cup '2, incident tothe rise in temperature necessary to fuse the disk 8 and make thecircuit closer operate, will not materially or even appreciably reducethis pressure of the spring 24- on the disk to and, therefore, will notin any way affect or slow up the operation of the circuit closer as awhole.

As hereinabove suggested, the connection of the thermostatic circuitcloser of the present invention to the fire alarm or other controlcircuit in which it is to be used may be effected in various ways, twoof which are illustrated in the drawings. In Figures 1 to 3 inclusiveare shown convenient means for connecting the circuit closer or thepresent invention to the two sides of an alarm or other circuit, thewires of which are concealed except at outlet boxes. As herein shown, acover 32 for a circular outlet box is preferably formed of insulatingmaterial such as Bakelite and is provided with two depending contactarms 34 and 35 which extend through openings 33 and so in said cover.The vertical arms 3 and 35? are respectively provided with right-angledor horizontal extensions 42 and M on the inside of the cover 32, intoconductive engagement with which binding post brackets 46 and 53 may beclamped by means of screws 50 tapped into the cover 32 itself. Eachbinding post bracket 46 and 48 may be provided with one or two clampscrews 52 for making connections with the respective sides of the firealarm or other control circuit.

Each of the depending or vertical arms 34 and 36 is provided with anopening 54 to receive the clamping jaws 4 and I6, the jaws It beingshown in Figure 1 as received in the opening 54 of the depending arm 35and the jaws 4 as received in the opening 54 of the depending arm 34. Asalso shown, the arms 34 and 3-8 are so spaced that, when the clampingjaws have been inserted in the openings therein and the screws 5% havebeen screwed down to clamp the binding post brackets 46 and 48 to thehorizontal extensions 42 and 44 and to secure these parts tightly to theinner wall of the cover 32, the thermostatic circuit closer will be heldtightly clamped between the arms 34 and 36 with the inner faces of thesearms in tight conductive relation to the shoulders 6 and 18.

In Figures 4 and 5 thermostatic circuit closers embodying the presentinvention are shown as constituting the fire detecting parts of a firedetecting cable. These cables are not usually concealed but may bestrung along the ceilings of any rooms or other spaces to be protected.

As hereinabove suggested, this fire detecting cable may comprise twowires 55 and 58, constituting respectively the two sides of a fire alarmor other circuit to be rendered operative by the circuit closer of thepresent invention, each of these wires being covered with flexible firere sisting insulation 60, preferably of one of the modern insulatingplastics, such, for example, as one of the vinyl plastics. In orderthat, as above suggested, the fire detecting cable need not be concealedbut may be exposed along the ceiling of any space to be protected, inpreparing the novel fire detecting cable of the present invention theinsulated wires 5t and 58 will prefanaaee erably be twisted togetherexcept at intervals :properly spaced for fire detecting purposes, wh chmay be, for example, when using the novel onportions thereof may beinserted between the jaws 4 and between the jaws [6, respectively, afterwhich the jaws may be clamped together as .shown in Figure 5, thuseffecting a good electrically conductive connection between the cirecuit closers and the two sides of the circuit.

As also pointed out hereinabove, it is important, in any fire preventionsystem using thermostatic circuit closing means, that the point at whichthe circuit has been closed shall be readily discernible. The difficultyof locating the point of operation has been one of the objections to theuse. of those fire detecting cables which are so constructed that thecircuit may be thermostatically closed at any point along their lengths.In order that the point at which the temperature rise has occurred andat which the thermostatic circuit closer has operated may readily bedetermined we provide each circuit closer, preferably in the closure end(which, for example, may be formed of a black Bakelite), whiclrindicating means E32, such, for example, as that disclosed in U. S.Letters Patent to John H. Derby, No. 1,938,583, granted December 12,1933, and which comprises a piece of fusible material, for example a waxor similar material, which dis plays a color in contrast to that of thematerial in which the cavity that contains the detecting material isformed. In this case, if a black Bakelite be used the wax or otherfusible material employed might be impregnated with powdered aluminumwhich upon fusion of the wax would give a white indication on theclosure end of the thermostatic circuit closer that had operated.

From the foregoing description or" fire detecting cable incorporatingtherein thermostatic circuit closers of the present invention it will beseen that, not only can this cable be easily manufactured and installed,but whenever any one of the thermostatic circuit closers has operated toclose the circuit it can readily be located and easily replaced withoutcutting the cable or otherwise disturbing its installation.

The embodiment of the invention shown in Figures 1 to 3 of the drawingsand the means there shown for supporting the circuit closer upon thecover of an outlet box and effecting a connection to the circuit in thebox are suitable for fire alarm and other control circuits operating atlow voltages, for example, voltages of from 14 to 40 volts. However, insome modern installations standard house voltages are used, in theneighborhood of 120 volts. In such cases it is not desirable to haveboth terminals exposed, as in the embodiment shown in Figures 1 to 3,since someone might accidentally take hold of or contact one terminalwith one hand and the other with the other and thus get an unpleasantshock. In Figures 6 and 7, therefore, is shown a slight modificationboth of the circuit closer construction and of the support thereforwhereby only one terminal is exposed in the space to be protected.

In the embodiment of the invention shown in Figures 6 and 7 the cup part2 of the circuit closer is constructed without the clamping arms 4 shownin Figure 1 of the drawings. Instead, it iszprovided at its upper endwith anqintegral flange 66 which serves both to support it on acountersunk ledge 61 surrounding an opening 68 in the outlet box cover10, formed of insulating material, and ,to provide a shoulder againstwhich a contact ring 12 may be pressed. The ring 72, which may bestamped out of a thin sheet of suitable electrically conductive metal,has integral with it a strap 14 which extends beneath the binding postbracket 46. The body of the cup part 2 of the circuit closer of Figure 6extends through the opening 68 into the space to be protected.

- The connection to the otherside of the circuit,in the modified form ofthe invention shown in Figures 6 and 7, is made bysubstitutingfortheclamping arms H5 at the upper end of the rod l4 of the Figure 1 forma split threaded end '15, above the shoulder l8, upon which may bescrewed a clamping nut 16 for clamping against the shoulder l8 a ring 18of a construction similar to the ring 12, the ring 18 having a strapextension which extends beneath the binding post bracket 43. Byspreading the two parts of the split part 75 of rod M the nut 16 may belocked in clamping relation to the contact ring 18. As in the form ofthe invention shown in Figure l, clamp screws 50, tapped into the outletbox cover l0, serve to clamp the binding post brackets 46 and 48 intogood conductive relation respectively to the straps l4 and 80 and thusto connect the cup 2 to one side of the alarm or other control circuitand the rod l4 to the other side of said circuit.

Except for the substitution of the means shown in Figure 6 forconnecting the cup 2 and conduc- .tive rod M to the two sides of thealarm or other control circuit the construction of the thermostaticcircuit closer shown in Figures 6 and '7 is substantially the same asthat shown in Figure l. The only additional change shown in Figure 6 isthe substitution of a separate disk 82 of insulating material, havingformed therein the well 30-, for the boss integrally molded with thedisk H] in which the well 30 is shown as formed in Figure 1 of thedrawings, this change being made for convenience and economy inmanufacturing the thermostatic circuit closers.

The cover TI) is preferably provided with the usual integrally moldedridge or ridges 8G for further insuring the insulation of the two sidesof the alarm or other circuit from each other. A like ridge indicated bythe same reference numeral will also be seen as constituting a part ofthe outlet box cover 32 in Figures 1 and 3 of the drawings.

What is claimed as new is:

1. In a thermostatic circuit closer, a thinwalled-cylindricalelectrically and thermally conductive cup having its-bottom connectibleto one side of a circuit-and having an insulating closure for its mouth,a relatively thin disk of conductive alloy, fusible at a predeterminedtemperature, covering the inside bottom of said cup, a piston-like diskof insulation, spring-pressed against and coextensive with the exposedface of the alloy disk and having a central opening therethrough intowhich the fused alloy may be forced by the pressure of said insulationpiston, a conductive rod having its exposed end connectible to the otherside ofsaid circuit, said rod extending coaxially through said cupclosure into said cup and into the upper end of the central opening insaid insulation-piston in fixed spaced relation to the unfused alloydisk and in substantially liquid- -tight relation. to the: upper. end ofsaid opening in all positions of relative movement of said insulationpiston and said rod.

2. A thermostatic circuit closer according to claim 1 in which the partof the opening adjacent to the fusible disk is of a diameter less thanthat of the rod and the insulating disk is provided with a well intowhich the conductive rod is telescopable to an extent sufiicient toinsure confinement of the fused alloy between said rod end and the cupbottom at all stages of the relative movement of said disk and said rod.

3. A thermostatic circuit closer according to claim 1 having a flangeabout its closure end, an outlet box cover of insulating material havinga countersunk opening therethrough for supporting said circuit closer byits flange, with the cup part thereof projecting into the space to beprotected, and means carried respectively by the cup and REFERENCESCITED The following references are of record in the 10 file of thispatent:

UNITED STATES PATENTS Number Name Date 794,497 Gould July 11, 1905796,904 Fiske Aug. 8, 1905 875,810 Hall Jan. 7, 1908 1,274,248 Derby eta1 July 30, 1918 1,935,611 Bourbon Nov. 21, 1933

